Off-peak water heating system



Oct. 7, 1941. c. M. osrERHELD 2,257,887

OFF-PEAK WATER HEATING SYSTEM Filed oct. '28, 1940 INVENTOR .CLARK UsrERf/ELD ATTORNEY Pstented Oct. 7,1941

n :,zsmsr oFF-PEAK WATER nEA'rmo SYSTEM Clark M. Osterheld, Stoughton, Wis., assigner to McGraw Electric Company, Elgin, lll., a corporation of Delaware Application October 28, 1940, Serial N0. 363,105

(Cl. 21S-39) 8 Claims.

My invention relates to electric water heating systems and particularly to off-peak water heating systems.

Une of the objects of my invention is to provide a relatively simple oil-peak water heating system embodying means for ensuring prolongation of the heating of the water after the end of an olf-peak period in case a predetermined amount of cold water is present in the tank at the end of an off-peak period.

Another object of my invention is to provide a water heating system including a time-controlled means cooperating with a tank water temperature controlled means to control the energization of the heater under ordinary operating conditions of use of hot water from a tank.

Other objects of my invention will either be apparent from a description of several forms of systems embodying my invention or will be pointed out in the course of such description and set forth in the appended claims.

In the single sheet of drawings,

Figure 1 is a view showing one diagram of connections as associated with a domestic hot water tank, and embodying my invention,

Fig. 2 is a fragmentary top view showing "the mechanical connections of certain parts of my system,

Fig. 3 is a fragmentary view in front elevation showing a certain setting of parts of a timer used in my system,

Fig. 4 is a view similar to Fig. 3 but showing the same parts in relatively different operating positions, and,

Fig. 5 is a schematic view of a modified form lof water heating system embodying my invention.

It has been found in actual practice that while an off-peak water heating system per se may be effective to meet most of the operating conditions to be met with in domestic use, occasions may arise when modifications of the ordinary system are necessary and useful and one of these modifications is the provision of relatively simple prolongation means for ensuring the continuation of the energization of the electric heater of a hot water tank beyond the end of an on-peak period in case the tank contains less than a predetermined amount oi hot water at the end of an off-peak period.

Referring first to Fig. 1 of the drawing, I have there shown a continuously operative timer II as embodying an electric synchronous motor il which is adapted to be energized from a pair of supply circuit conductors i5 and l1 which may re- 55 one.

ceive electric energy from a suitable central power station operating continuously. The motor i3 will therefore operate continuously and is provided with a worm gear i9 meshing with a worm wheel 2 i. which worm wheel is mounted on a shaft 23. The shaft 28 is to be understood as being suitably supported by bearings not shown in the drawing, so that the continuously operative motor will cause one complete rotation of the disc 2i nd the shaft 23 in the twenty-four hours of a A cam disc 25 is adjustably mounted on the shaft 23 and has two different outer radii, a pertion 21 of the periphery having a somewhat larger radius than that of the portion 25. The part 21 of the disc 25 is shown as extending substantially one-third of the total peripheral length of the disc 25, that is, it will correspond to an offpeak period of substantially eight hours. The position of the cam disc 25 shown in Fig. l is that which, for illustrative purposes. is occupied by the disc at 10:00 p. m., which we may consider to be the start of an offpeak period which will therefore and at substantially 6:00 a. m. It is to be understood, however, that changes may be made in not only the duration of an off-peak period as provided by the peripheral extent of part 21 but also that the start and the end of an off-peak period may be changed in accordance with the ideas of the engineers of the utility supplying current to the supply circuit conductors I5 and I1.

The system particularly embodying my invention is adapted to be applied to a hot water tank 29, which is here shown as of the elongated circular or cylindrical type usually used in homes. The tank 29 is provided with a cold water inlet pipe 3i secured to the tank at the bottom thereof and with a hot water outlet pipe 33 connected therewith at 'the top portion thereof. A mass 35 of heat insulating material may surround the tank 29 and an outer casing 31 is adapted to hold the heat insulation in its proper operating position relatively to the tank 29. The tank may be supported by legs 39, all in a manner well known in the art, and while I have shown certain details of an ordinary domestic hot water tank, my invention is not limited to these details which are shown for illustrative purposes only.

An electric heater 4I may be provided and I have shown it as being positioned in a tunnel 43 and extending annularly around the tank 29' near the bottom thereof but I desire it to be understood that this position is not an essential I provide a thermally actuableheater control switch 45 which, for illustrative purposes, is shown as embodying a tubular member 41 secured to a wall of the tank 25 in a mud-tight manner f be moved out of engagement with contact arm 5| when tubular member 41 is surrounded by hot water. I use the term hot" to describe water which has been heated to a selected relatively high temperature such as is usually used in a home.

1 provide a main timer-@ontrouw switch Ini` which comprises a relatively rigid contact arm 51 and a resilient contact arm 59 normally biased 20 out of engagement with contact arm 51 but moved into engagement therewith when a. small lug 6|, of electric insulating material, on contact `arm 58 is engaged by the part 21 of cam disc 25.

Switch 55 is shown in its closed position which it is intended to occupy at the start of an cifpeak period, irrespective of the time at which such engagement may be effected, as hereinbefore set forth, and is to be held in closed position during an off-peak period only.

Supply circuit conductor I5 is connected by a conductor 63 with contact arm 55 while contact arm 51 is connected by a conductor 65 with one terminal of the heater 4|. 'I'he other terminal of heater 4| is connected by a conductor 51 with 35 resilient contact arm 53 of switch 45. Contact arm 5| is connected by a conductor 6B with the other supply circuit conductor |1.

If it be assumed that the tank content is not all hot. that is, that thermally-responsive switch 45 is subject to cold water at the start of' an oil'- pcak period, an energizing circuit through heater 4| will be closed as follows: From conductor |5 through conductor 63, the engaged contact members 59 and 51, through conductor B5, the heater 4|, through conductor 51, through the engaged contact members 53 and 5|, then through conductor 69 to the other supply circuit conductor I1. It is thus obvious that energization of the heater 4| will be effected at the start of an onpeak period in case of the presence of an appreciable quantity of cold water at the start of an off-peak period and that should all or substantially all of the water in the tank be heated to a desired temperature within the duration of an off-peak period, thermally actuable switch 45 will cause disengagement of contact arms 5I and 5| and consequent deenergization of the heater. It is further evident that should withdrawals of hot water from the tank occur during the rest of the off-peak period after deenergization of the heater 4|, as above described, thermally actuable switch 45 will effect reenergization of the heater 4| to cause heating of the water in the manner well known in the art.

I desire to vhere point out that while I have shown specific positions of the heater 4|, and of the thermally actuable switch 45, I do not desire to be limited thereto but may so cooperatively position these two elements of my system that the heater 4| will be deenergized only when all or substantially all of the water in the tank has been heated to the desired temperature, generally designated by the term hot.

Ict it be assumed that the withdrawals of hot water reduced the amount of hot water in the tank to such an extent that all of the water in the tank was not heated to the desired temperature at the time of termination of an ofi-peak period. In order to prolong the energization of the heater I provide an electromagnetic prolongation switch and means to control the same according to time and accordingto tank water temperature.

For this purpose an electromagnetic switch 1| is provided which includes a coil 18, a magnetizable core member 1l, a pair of fixed contact members 11 and a cooperating contact bridging member 1l, all of these elements being well known in the art and I have. therefore, illustrated them generally only. I provide further an auxiliary timer-controlled switch 8| which switch includes a relatively rigid contact arm Il and a resilient contact arm I5 normally yieldingly-biased out of engagement with contact arm II as shown in Fig. 1 of the drawing. Timer-controlled means to actuate the switch Il and particularly a lug 55, of electric-insulating material on the arm I5 thereof, includes an'auxiliary cam disc I1 adjustably mounted in front of cam disc 25. Cam disc l1 has a predetermined peripheral portion Il thereof of greater outer radius than the rest of the peripheral surface of thecam disc and it may be assumed, for instance, that the time extent of part Il of disc 51, having a greater outer radius, is on the order of three or four hours. The disc l1 is shown as in a position to cause substantially full prolongation provided by the peripheral portion Il but it may be peripherally adjusted relatively to cam disc 25 and held in such position by a small set screw Il which is adapted to have screw-threaded engagement with short stud 5I integral with or secured to the front surface of cam disc 25. as shown more pa'rticularly in Fig. 2 of the drawing.

Contact arm 55 is connected to one of the fixed contact members 11 by a conductor 55 and the other ilxed contact member 11 is connected by a conductor 51 with conductor 55. One terminal of coil 13 is connected to that fixed contact 11 which has conductor l1 connected therewith, and the other terminal of coil 13 is connected by a conductor 5S to contact arm Il. Contact arm is connected by a conductor III with contact arm 5I and therefore also to conductor 51.

Let it be assumed that contact arms l5 and Il have been moved into engagement with each other a short time before the end of the off-peak period, that is, a short time before disengagement of contact arms 5I and 51 from each other, whereby a prolongation energizatlon circuit will be established as follows, by the action of the electromagnetic contactor 1|. The energizing circuit through coil 1I may be traced as follows: From conductor |5 through conductor Il, through engaged contact arms 5l and 51, through conductors 65 and l1, through coil 1l. through conductor l5, through engaged contact arms Il and Il, through conductor III, through engaged contact arms 5I and 5| and from there through conductor Il to the other supply circuit conductor |1. This will cause magnetization of the core 15 and resultant upward movement of the core 15 and of the contact bridging member 19 into engagement with the fixed contact members 11. This will cause closing of a heater-energizing circuit traceable as follows: From supply circuit conductor |5 through conductors 55 and l5, through engaged contact members 11 and 1I, through conductors I1 and 55, through heater 4|,

through conductor 81, through engaged contact arms- 58 and 5| and from there through conductor 59 to the other supply circuit conductor I1. Under the assumed conditions that thermally actuable switch 45 is subject to the temperature of relatively cold water, as hereinbefore stated, this energizing circuit will continue even after contact arm 59 has been moved out of engagement with contact arm 51 by reason of the turning movement of part 21 of disc 25 out of engagement with the knob 5I on contact arm 59. A holding circuit for the coil 13 oi' the electromagnetic switch 1| may be traced as follows: From supply circuit' conductor i5 through conductors 83 and 95, through engaged contact members 11 and 19, through coil 13, through conductor 99, through engaged contact arms 83 and 85, through conductor |I, through engaged contact arms 53 and 5| and from there through conductor 89 to the other supply circuit conductor l1. It is evident that this holding circuit for the coil 13 is independent of the main timer-controlled switch 55 so that energization of the heater 4| will continue beyond the end of an off-peak period, at which time the main timer-controlled switch was opened, this energization continuing until the thermally actuable switch 45 is subject to the temperatureof hot water in the tank and causes disengagement of its contact arms with resultant deenergization of the heater when substantially all of the water in the tank is hot.

Reference to Fig. 3 of the drawing is here made as showing the position of the main and of the auxiliary timer-controlled switches 55 and 8| just before the end of an ofi-peak period when the main timer-controlled switch 55 is still closed and the auxiliary timer-controlled switch 8| has also been closed, all as hereinbefore described.

Reference to Fig. 4 of the drawing will show another position into which the auxiliaryvcam 81 may be moved manually to prevent any overrun if, for any reason, the operator or user of this system may desire such operation.

The system shown in Fig. 1 of the drawing is, as has already been set forth, effective to cause prolongation of the energization of the tank heater in case all of the water in the tank is not hot at the end of an off-peak period. I have illustrated, in Fig. 5 of the drawing, a modified system in which prolongation of the energization of the heater 4| is effected in case a predetermined fractional part of the total water content of the tank is cold or to put it in another way, in

which less than a predetermined fractional part of the water content of the tank is hot at the end of an otr-peak period.

In this modified system I provide an auxiliary thermally actuable switch |03 here illustrated as including a tubular member |05 secured to the wall of the tank 29 in a iiuid-tight manner to be positioned inside of the tank, an expansion rod |01, a relatively rigid contact arm |09 and' a resilient contact arm I normally yieldingly biased into engagement with arm |09 but moved out of engagement therewith by the expanded rod |01 when tubular member |05 is surrounded by hot water or by water having a selected relatively high temperature. Contact arm |09 of switch |03 is connected by a conductor I 3 with contact arm 5| and also to one terminal of heater 4|. Contact arm Il is connected by conductor H5 with contact arm 85 of the auxiliary timer-controlled switch 8|.

The operation oi this modified system is substantially as follows: Let it be assumed that, at the start of an off-peak period, when the continuously operative timer and particularly the main and the auxiliary cam discs and 81 are in the positions shown in Fig. 5 of. the drawing, the main thermally actuable heater-controlled switch 45 was surrounded by cold water, that is, all of the water in the tank was not hot. Energization of the heater 4| would then be effected as hereinbefore described and would continue until thermal switch 45 was subject to the temperature of hot-water when it would effect disengagement of contact arms 5| and 53 from each other with resultant deenergization of the heater 4 I. Should .withdrawals of hot water occur during the rest of the oil-peak period suloient to subject tubular member 41 to cold water, reenergization of the heater 4I would be effected.

Let it now be assumed that withdrawals of hot water from the tank occur during the last part of an oil-peak period to such an extent that auxiliary thermally actuable switch |03 is subjected to cold water with resultant engagement of contact arms |09 and I|| with each other. When the knob on contact arm 85 engages portion 89 of disc 81 just before the end of an oli-peak period, closure of the switch 8| will be effected and under the assumed condition of engagement of contact arms |09 and a prolongation energization circuit will be closed by the action of prolongation switch 1| energized through a circuit as follows: From supply circuit conductor I5 through conductor 83, through engaged contact arms 59 and 51. through conductors 55 and 91, through one of the fixed contact members 11, through coil 1|, through conductor 99, through engaged contact arms 83 and 85, through conductor ||5, through engaged contact arms and |09,`through conductor |I3 and through engaged contact arms 5| and 53 and from there through conductor 59 to the other supply circuit conductor |1. This causes energization of the core 15 and resultant upward movement of it and of the contact bridging member 19 whereby an auxiliary heater-energizing circuit is closed as follows: From supply circuit conductor I5 through conductors 53 and 95, through engaged contact members 11 and 19, through conductors 91 and 65, through heater 4|, through conductor ||3, through engaged contact members 5| and 53 and from there through conductor 69 to the other supply circuit conductor |1. It is obvious, of course, that if Athe upper auxiliary thermally actuable switch |03 is surrounded by cold water, the lower main thermally actuable switch 45 is also surrounded by cold water. A holding circuit for the coil 13 is also closed as follows: From supply circuit conductor I5 through conductors 53 and 95, through engaged contact members 11 and 19, through coil 13, through conductor 99, through engaged contact arms 83 and 85through conductor ||5, through engaged contact arms and |09, through conductor ||3, through engaged contact arms 5| and 53 and from there through conductors 69 to the other supply circuit conductor l1. This holding circuit will continue in its closed condition until disengagement of contact arms 85 and 83 at the end of the adjustably preset fixed length of a prolongation period when contact arm 85 moves out of operative engagement with the part 89 of larger outer radius.

It is thus evident that my system. in its several modications, provides means for initiating the energization oi.' the electric heater of a hot water tank at the start oi an oil-peak period unless all of the water in the tank is already hot and further provides for deenergisation of the heater at any time during an oil-peak period in case substantially al1 of the water content of the tank is hot. It further provides means for prolonging the energization oi the heater beyond the end oi' an oir-peak period in case the tank contains less than a predetermined quantity of hot water at the end of an oir-peak period and this over-run or prolongation of the energization oi the heater is adapted to extend for an adjustably predetermined ilxed length of time. Ii the predetermined amount of hot water is present in the tank before the end of the prolongation period. the heater will be deenergized. but the energization of the heater will be prolonged only to the end oi said preset prolongation period, deenergization of the heater then occurring irrespective ai how much hot water is in the tank provided it is less than either a predetermined fractional part ci the total water content or less than the tctal water content of the tank.

I have illustrated a particular position oi' the auxiliary thermally actuable switch as regards the height of the tank but I do not desire to be limited to this particular position since the auxiliary thermal switch of Fig. 5 of the drawing may be positioned at any point in the tank and the hereinbefore mentioned predetermined iractional part of the total water content oi the tank will vary in accordance therewith so that I may ensure that the tank is at least illed with onethird of its total contents with hot water, onehalf or two-thirds, all in accordance with the position oi.' the auxiliary thermally actuable switch |03.

Various further modifications may be made in the systems embodying my invention and all such modifications clearly coming within vthe scope of the appended claims are to be considered as being covered thereby.

I claim as my invention:

l. An oil-peak water heating system for a hot water tank having an electric heater, comprising a plurality of heater control switches controlled respectively and jointly by tank water temperature and by time-controlled means effective to cause energization of the heater at the start of an oil-peak period if the tank contains an appreciable quantity of cold water at that time and to continue the energization o1'. the heater for a preset length of time after the end of an ot!- peak period in case of the presence of a predetermined quantity of cold water in the tank at the end of an oil-peak period.

2. An oil-peak water heating system for a hot water tank having an electric heater, comprising a pair of heater control switches severally controlling the energization of the heater in accordance with time and tank water temperature and effective to start energization of the heater at the start of an oil-peak period in case the tank is less than full of hot water and to stop energization of the heater during an oir-peak period when all of the water in the tank is hot and -another heater control switch controlled lointly by time and the temperature of the water at a predetermined point in the tank to prolong the energization of the heater for a fixed length of time after the end of an off-peak period in case the temperature of the water at said predetermined point is below a certain value at the end of an oil-peak period.

3. An oil-peak water heating system for a hot atmet? water tank having an electric heater, comprising a continuously operative timing means, a heater control switch movable to heater-energizing position-by the timing means at thc start of an oil-peak period. a thermally actuable heater control switch electrically connected in series circuit relation relatively to the iirst named switch, responsive to tank water temperature and maintained in heater-energizing position until substantially all of the water in the tank is hot, said switches cooperating to start energization of the heater at the start oi an oil-peak period in case the tank contains an appreciable amount of cold water at the start oi an oil-peak period and to cause deenergization of the heater during the oir-peak period when substantially all oi the water in the tank is hot and a third switch controlled jointly by the timing means and by tank water temperature to cause prolongation oi' the energization oi the heater for a nxed length of time beyond the, end oi an oil-peak period in case oi the presence of a predetermined amotmt of cold water in the tank at the end o! an oil-peak period.

4. An oil-peak water heating system for va hot water tank having an electric heater, comprising a plurality oi heater control switches controlled respectively and jointly by tank water temperature and byl time-controlled means effective to cause energization oi the heater at the start of an oil-peak period if the tank contains an appreciable quantity of cold water at that time, to cause deenergization of the heater at any time during an olf-peak period in case substantially all of the water in the tank is hot, to cause reenergization of the heater in case of withdrawal of an appreciable quantity of hot water from the tank during the rest of an oft-peak period and to continue the energization oi the heater for a preset length of time after the end of an oi!- peak period in case oi.' the presence of a predetermined quantity of cold water in the tank at the end of an oil-peak period.

5. An oir-peak water heating system for a hot water tank having an electric heater, comprising a continuously operative timer. a heater control switch movable into closed position by said timer at the start of an olf-peak period and held in closed position thereby during an oil-peak period, a normally-closed tank water temperature responsive heater control switch movable into heater-deenergizing position when substantially all of the water in the tank is hot, an electromagnetic switch having its contacts electricalLv connected in shunt circuit with the timer-controlled switch, an auxiliary switch moved into closed position by said timer before the end of an oil-peak period and held in closed position thereby during a preset fixed length o! time after the end of an oil-peak period and electric connections between all of said switches to cause energization of the heater at the start of an oilpeak period and the closure of the timer-oontrolled switch in case of the presence of an appreciable quantity of cold water in the tank at the start 0i' an oil-peak period, to cause deenergization oi the heater when substantially all of the water in the tank is hot, to cause reenergization of the heater during the rest of the oil-peak period in case withdrawals of hot water from the tank reduce the quantity of hot water in the tank to below a predetermined quantity and to continue the energization oi the heater for`an adjustably preset length of time beyond the end oi an otr-peak period in case the quantity oi hot .a normally-closed tank water temperature responsive heater control switch movable into heater-deenergizing position when substantially all f the water in the tank is hot, an electromagnetic switch having its contacts electrically connected in shunt circuit with the timer-controlled switch,v

an auxiliary switch moved into closed position by said timer before the end of an off-peak period and held in closed position thereby during a preset fixed length of time after the end of an off-peak period and electric connections between all of said switches to cause energization of the heater at the start of an ofi-peak period and the closure of the timer-controlled switch in case of the presence of an appreciable quantity of cold water in the tank at the start of an oilpeak period, to cause deenergization of the heater when substantially all of the water in the tank is hot, to cause reenergization of the heater during the rest of the off-peak period in case withdrawals of hot water from the tank cause the presence of said appreciable quantity o! cold water in the tank and to cause prolongation of the energization of the heater beyond the end of an olf-peak period for an adjustably predetermined length of time in case of the presence of at least said appreciable quantity of cold water in the tank at the end of an off-peak period. c

7. An oit-peak water heating system for a hot water tank having an electric heater, comprising a continuously operative timer, a heater control switch movable into closed position by said timer at the start of an off-peak period and held in closed position thereby during an off-peak period, a normally-closed tank Water temperature responsive heater control switch movable into heater-deenergizing position when substantially all of the -water in the tank is hot. an electromagnetic switch having its contacts electrically connected in shunt circuit with the timer-controlled switch, an auxiliary switch moved into closed position by said timer before the end of an oit-peak period and held in closed position thereby during a preset fixed length of time after the end of an off-peak period and electric connections between all of said switches to cause energization of the heater at the start of an oipeak period and the closure of the timer-controlled switch in case of the presence of an appreciable quantity of cold water in the tank at the start of an off-peak period, to cause deenergization of the heater when substantially all of the water in the tank is hot, to cause reenergization of the heater during the rest of the off-peak period in case withdrawals of hot water from the tank cause the presence of said appreciable quantity of cold water in the tank and to cause prolongation of the energization of the heater beyond the end of an off-peak period for an adjustably predetermined length of time in case the tank is more than half full of cold water at the end of an oli-peak period.

8. An off-peak water heating system for a hot Water tank having an electric heater, comprising a continuously operative timerI means including a main timer-actuated heater control switch movable into closed position at the start of an offpeak period and into open position at the end of an off-peak period and effective to cause energization of the heater at the start of an off-peak period in case of the presence of an appreciable amount of cold water in the tank at the start of an off-peak period, an electromagnetic heater control switch electrically connected in parallel circuit relation with said timer-actuated heater control switch and an auxiliary timer-actuated switch electrically connected with said other switches and movable into closed position before the end of an off-peak period by the timer and effective to cause closing of the electromagnetic switch and continuance of the energization of the heater for a fixed duration beyond the end of the olf-peak period in case of the presence of a predetermined quantity of cold water in the tank at the end of an off-peak period.

CLARK M. OSTERHELD. 

